The Covalent Bond Classification (CBC) website
The covalent bond classification (CBC) method is a way to count electrons for transition metal compounds. It classifies ligands based on their type, either L, X or Z. This is the website for all things CBC. It contains a library which list useful materials for teaching CBC including books that teach the CBC method. The site also has teaching materials that contain MLX plots for all of the transition metals. The MLX plots are charts that show various electron counts and valence for a given metal.